PA28 proteasome-activator complex §

Is a 6/7 membered ring composed of PA28α and PA28β, both of which are induced by IFN-γ. A PA28 ring can bind to either end of the proteasome’s 20S core in place of the 19S caps, and acts to increase the rate at which peptides are released. In addition to simply providing more peptides, the increased rate of flow allows potentially antigenic peptides to escape additional processing that might destroy their antigenicity.

![[CleanShot 2023-12-10 at 16.12.33@2x.png]] The heptamer PA28 proteasome activator (yellow) interact with the α subunits at either end of the core proteasome. The α-annulus (in green), a narrow opening that is normally blocked by α subunits, without PA28 bound. Panel C shows the α-annulus with PA28 bound, it changes the conformation of the α subunits, and opens the end of the cylinder.